I have been trying this for a couple of weeks and if I do short intervals eg. 10 x 1 min it definitely gets the heart rate up. I have also used the elliptical (no impact but still weight-bearing) but don't get the same feeling of 'running' from that.
I bought a belt from the swimming teachers association website for £14. I thought I'd feel a bit daft in the pool but no problem at all. Give it a go!